The present invention relates to a superconductive device for helping shield magnetic field as well as to a method for manufacturing such a superconductive device.
Ferromagnetic materials such as permalloy or ferrite has been utilized to reduce the effects of magnetic field into that of a certain space. Currently many devices have been introduced to help shield magnetic field by Meissner effect of superconductors. For example, in Japanese Patent Laid Open No. 1-134998 (1989) superconductive materials are arranged to the innermost side of the space in which the magnetic field is shielded. In U.S. patent application Ser. No. 509,438 a superconducting magnetic shielding tube, i.e. a tube for shielding magnetic field, has been proposed by the present applicants that comprises at least two layers which include a layer of a substrate and a layer of superconductor arranged in this order from the magnetic source to be shielded.
As the structure of superconductive oxides becomes larger due to a demand of its application, it becomes more difficult to integrally form a structure of superconductive oxides and to form a homogeneous layer of superconductive oxide. Besides, it is not industrially preferable to enlarge the apparatus for manufacturing them. Therefore, the necessity is growing to prepare structures of superconductive oxide and combine them later.
However, a large device for helping shield magnetic field using superconductive oxide for actual practice has still remained in a developing stage at present mainly due to a problem in connecting layers of superconductive oxide. Magnetic field has been known to leak through joints in conventional methods of joining the layers, and high performance in shielding magnetic field cannot be achieved due to the leak.